1. Field of the Invention
The present invention relates to integrated circuits, control methods, and related LED lighting systems.
2. Description of the Prior Art
Light-emitting diodes (LEDs) have a very good electro-optical conversion rate, which is higher than fluorescent lamps, cold-cathode fluorescent lamps, and light bulbs. Thus, the current trend is to replace these types of lamps with LEDs. For example, LEDs have already gradually replaced CCFLs as a backlight source in liquid crystal display (LCD) panels.
When using LEDs as a backlight source for an LCD panel, due to the LCD panel's large area, a very large number of LEDs must be used, and these LEDs are normally arranged in chains, each chain driven by a controllable current source. Current flowing through each LED chain is controlled to be the same, so that brightness of all LEDs is approximately the same. If light emitted by each LED is given appropriate propagation, brightness of the LCD panel will be reasonably even.
However, if even one LED out of all LEDs in the LCD panel is short-circuited or open-circuited, the LCD panel brightness will be uneven. Thus, a good LED chain driving circuit should have appropriate sensing circuitry to sense whether any LEDs are open- or short-circuited, and take appropriate preventative measures.
The moment an LED chain driving circuit is connected to power, it is highly probable that, because driving power is not ready, the LED chain driving circuit will determine that the LED chain cannot be driven, which causes an erroneous open-circuit or short-circuit determination, which should be avoided.